U.S. patent application number 15/869014 was filed with the patent office on 2018-07-12 for flexible high-density memory module.
The applicant listed for this patent is Hany Mohamed Fahmy. Invention is credited to Hany Mohamed Fahmy.
Application Number | 20180196763 15/869014 |
Document ID | / |
Family ID | 62783092 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180196763 |
Kind Code |
A1 |
Fahmy; Hany Mohamed |
July 12, 2018 |
FLEXIBLE HIGH-DENSITY MEMORY MODULE
Abstract
A flexible high-density memory module for use with an electronic
computing device includes an interposer and a controller supported
on a first substrate, a number of SDRAM modules operably arranged
on a second substrate and a flexible substrate forming an
electrical connection between the interposer supported on the first
substrate and the SDRAM modules supported on the second substrate.
The controller and the interposer supported on the first substrate
is configured to electrically connect with a number of processor
interconnects supported on the main rigid printed circuit board of
the electronic computing device to provide a number of plug and
play, flexible, high density memory channels of desired capacities
utilizing the SDRAM modules supported on the second substrate. The
flexible substrate enables parallel, perpendicular and angular
placement of the SDRAM modules over a plane of the main rigid
printed circuit board, enabling optimal routing and
performance.
Inventors: |
Fahmy; Hany Mohamed;
(Bertem, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fahmy; Hany Mohamed |
Bertem |
|
BE |
|
|
Family ID: |
62783092 |
Appl. No.: |
15/869014 |
Filed: |
January 11, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62445597 |
Jan 12, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11C 5/04 20130101; G06F
13/1668 20130101; G11C 5/06 20130101 |
International
Class: |
G06F 13/16 20060101
G06F013/16; G11C 5/04 20060101 G11C005/04; G11C 5/06 20060101
G11C005/06 |
Claims
1. A flexible high density memory module for use with a plurality
of electronic computing devices comprising: a) at least one
interposer having a plurality of interposer interconnects supported
on a first substrate, the plurality of interposer interconnects
being configured to form at least one connection with a plurality
of processor interconnects supported on a main rigid printed
circuit board; b) at least one controller supported on the first
substrate; c) a plurality of SDRAM modules operably arranged on a
second substrate; and d) at least one conductive trace supported on
a flexible substrate having a first end and a second end, each
having a plurality of connectors, for forming an electrical
connection between the interposer supported on the first substrate
and the plurality of SDRAM modules supported on the second
substrate; whereby the controller and the interposer supported on
the first substrate is configured to electrically connect to the
plurality of processor interconnects supported on the main rigid
printed circuit board of the electronic computing device to provide
a plurality of plug and play, flexible, high density memory
channels of desired capacities utilizing the plurality of SDRAM
modules supported on the second substrate.
2. The flexible high-density memory module of claim 1, wherein the
first substrate supporting the interposer and the controller is a
first rigid printed circuit board.
3. The flexible high-density memory module of claim 2, wherein the
interposer and the controller are supported on one side of the
first rigid printed circuit board.
4. The flexible high-density memory module of claim 2, wherein the
interposer and the controller are supported on opposite sides of
the first rigid printed circuit board.
5. The flexible high-density memory module of claim 1, wherein the
second substrate supporting the plurality of SDRAM modules is a
second rigid printed circuit board, wherein the second rigid
printed circuit board is provided with a large surface area
compared to the first rigid printed circuit board.
6. The flexible high-density memory module of claim 1, wherein the
flexible substrate supporting the plurality of conductive traces is
a flexible printed circuit board, wherein the plurality of
connectors at the first end of the conductive traces connects to
the interposer and the controller supported on the first substrate,
wherein the plurality of connectors at the second end of the
conductive traces connects to the plurality of SDRAM modules
supported on the second substrate.
7. The flexible high-density memory module of claim 1, wherein the
controller supported on the first substrate is configured to
communicate with the plurality of SDRAM modules supported on the
second substrate through the conductive traces supported on the
flexible substrate.
8. The flexible high-density memory module of claim 1, wherein the
plurality of SDRAM modules supported on the second substrate forms
a plurality of dual in-line memory modules (DIMM) of desired
capacity capable of operating at a desired frequency.
9. The flexible high-density memory module of claim 1, is
configured to function in form of a plurality of plug and play
memory channels for the plurality of electronic computing
devices.
10. The flexible high-density memory module of claim 1, wherein the
flexible substrate enables a parallel placement of the plurality of
SDRAM modules over the main rigid printed circuit board of the
electronic computing device enabling optimal utilization of a
surface area of the main rigid printed circuit board.
11. The flexible high-density memory module of claim 1, wherein the
flexible substrate enables a perpendicular placement of the
plurality of SDRAM modules over the main rigid printed circuit
board of the electronic computing device enabling optimal
utilization of the surface area of the main rigid printed circuit
board.
12. The flexible high-density memory module of claim 1, wherein the
flexible substrate enables an angular placement of the plurality of
SDRAM modules over the main rigid printed circuit board of the
electronic computing device enabling optimal utilization of the
surface area of the main rigid printed circuit board.
13. The flexible high-density memory module of claim 1, wherein the
flexible substrate with a plurality of layers enables optimal
performance of the plurality of SDRAM modules by preventing
cross-talk between a plurality of components associated with the
main rigid printed circuit board.
14. The flexible high-density memory module of claim 14, wherein
the flexible substrate enables optimal performance of the plurality
of SDRAM modules by providing optimal heat dissipation with the
optimal selection of the bend angle and the bend radius.
15. The flexible high-density memory module of claim 1, enables
optimal routing and performance of a plurality of SERDES channels
associated with the main rigid printed circuit board of the
electronic computing devices by supporting the SDRAM modules on the
second substrate.
16. An electronic computing device, comprising: a) a processor
having a plurality of processor interconnects supported on a main
rigid printed circuit board; b) a plurality of conductive paths
provided on the main rigid circuit board to enable a plurality of
connections between the processor and a plurality of components via
the plurality of processor interconnects; and c) a flexible high
density memory module comprising: i. at least one interposer having
a plurality of interposer interconnects supported on a first
substrate configured to form at least one connection with the
plurality of processor interconnects; ii. at least one controller
supported on the first substrate; iii. a plurality of SDRAM modules
arranged on a second substrate; and iv. a flexible substrate
supporting at least one conductive trace having a first end and a
second end, each having a plurality of connectors, for forming an
electrical connection between the interposer interconnects and the
plurality of SDRAM modules; whereby the processor communicates with
the plurality of SDRAM modules through the conductive traces
provided on the flexible substrates.
17. The electronic computing device of claim 16, wherein the
flexible high density memory module is connected to the main rigid
printed circuit board using the plurality of interposer
interconnects supported on the first substrate.
18. The electronic computing device of claim 16, wherein the first
substrate supporting the interposer and the controller is a first
rigid printed circuit board, wherein the first rigid printed
circuit board is configured to support the interposer and the
controller on a same surface and on opposite surfaces.
19. The electronic computing device of claim 16, wherein the
flexible high-density memory module is a plug and play memory
module.
20. The electronic computing device of claim 16, wherein the
flexible substrate of the flexible high-density memory module
enables: a parallel placement of the plurality of SDRAM modules
arranged on the second substrate over a plane of the main rigid
printed circuit board; a perpendicular placement of the plurality
of SDRAM modules arranged on the second substrate over a plane of
the main rigid printed circuit board; and an angular placement of
the plurality of SDRAM modules arranged on the second substrate
over a plane of the main rigid printed circuit board; wherein the
flexible high-density memory module optimizes a surface area
utilization of the main rigid printed circuit board by placing the
plurality of SDRAM modules arranged on the second substrate over
the main rigid printed circuit board; wherein the flexible
substrate, of the flexible high-density memory module, connecting
the first substrate to the second substrate enables: an optimal
surface area utilization of the main rigid printed circuit board;
an optimal heat dissipation from the plurality of SDRAM modules; an
optimal performance of the plurality of SDRAM modules; and an
optimal routing and performance of a plurality of SERDES channels
associated with the main rigid printed circuit board.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is related to and claims priority
from prior provisional application Ser. No. 62/445,597, filed Jan.
12, 2017 which application is incorporated herein by reference.
COPYRIGHT NOTICE
[0002] A portion of the disclosure of this patent document contains
material which is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent file or records, but otherwise
reserves all copyright rights whatsoever. 37 CFR 1.71(d).
BACKGROUND OF THE INVENTION
[0003] The following includes information that may be useful in
understanding the present invention(s). It is not an admission that
any of the information provided herein is prior art, or material,
to the presently described or claimed inventions, or that any
publication or document that is specifically or implicitly
referenced is prior art.
1. Field of the Invention
[0004] The present invention relates generally to flexible
high-density memory modules. More specifically, the present
invention relates to a flexible high-density memory module with a
number of high-density memory modules supported on a rigid
substrate positioned away from a main circuit board of embedded
computing devices.
2. Description of the Related Art
[0005] The miniaturization of hardware forces the engineers to use
the highest performance setting for every component placed on a
compact printed circuit board with minimal power consumption.
Unfortunately the standard of low power low voltage technology used
in the modern printed circuit board designs increase the problem
related to signal and power integrity. Actually a DDR4 and LPDDR4
memory modules can run at the maxim rate of 3.2 GT/s. This kind of
memory is often found in most common devices that we use in our
day-to-day life. Most of the existing companies have as one main
target, which is to produce high-speed devices and, at the same
time, with lower consumption, lower dimension and lower prize.
Embedded systems such as SBCs, ADAS and infotainment systems adopt
memory-down as the sole architecture for memory channels such as
DDR3, DDR4 and LPDDR4. This has the advantage of improved signal
integrity and a compact design compared to using DIMM sockets.
However, such memory-down architecture consumes large space or real
estate on the PCB, especially when high-density memory, such as
with 36-sdrams, is required. The memory devices with conventional
memory-down architecture consume more than 30% of PCB surface area.
This provides a challenge to route other signals such as SERDES
channels through the PCB without increasing the layer-count and at
the same time meeting the cost and performance targets. In
addition, in designing such a system, the performance of the DDR4
and LPDDR4 high density SDRAMs to be installed on the circuit
boards of such systems cannot be compromised.
[0006] Prior attempts have been made to provide high density SDRAMs
that occupies less space in the main PCB. Traditional SDRAM dual
inline memory modules (DIMMs) are simply too tall to be able to be
mounted vertically on the system board. Special sockets have been
designed to allow DIMMs to be mounted either at an angle or even
parallel to the system board. As the speed of memory devices
increases to greater than 200 megahertz, for example, the
electrical performance of such DIMM sockets is becoming inadequate.
Further the placement of DIMM sockets on the main PCB poses serious
challenge to the embedded designers to route other signals such as
SERDES channels through the PCB without increasing the layer-count
and at the same time meeting the cost and performance targets. The
following prior arts are hereby incorporated by reference for their
supportive teachings of the present invention.
[0007] U.S. Pat. No. 6,545,895 titled "High capacity SDRAM memory
module with stacked printed circuit boards" issued to High
Connection Density, Inc. discloses a family of memory modules with
granularity, upgradability, and a capacity of two gigabytes uses
256 MB SDRAM or DDR SDRAM memory devices in CSPs in a volume of
just 4.54 inches by 2.83 inches by 0.39 inch. Each module includes
an impedance-controlled substrate having contact pads, memory
devices, and other components, including optional driver line
terminators, on its surfaces. The inclusion of spaced, multiple
area array interconnections allows memory devices to be
symmetrically mounted on each side of each of the area array
interconnections, thereby reducing the interconnect lengths and
facilitating the matching of interconnect lengths. Short area array
interconnections, including BGA, PGA, and LGA options or
interchangeable alternative connectors provide interconnections
between the modules and the rest of the system. Thermal control
structures may be included to maintain the memory devices within a
reliable range of operating temperatures.
[0008] Another prior art, U.S. Pat. No. 7,379,316 titled "Methods
and apparatus of stacking DRAMs" issued to Metaram, Inc. discloses
a memory device for electrical connection to a memory bus, the
memory device comprises a number of dynamic random access memory
("DRAM") integrated circuits, stacked in a vertical direction, each
DRAM integrated circuit comprising a memory core of a number of
cells and accessible at a first speed and an interface integrated
circuit electrically coupled to the number of DRAM integrated
circuits for providing an interface between the DRAM integrated
circuits and the memory bus at a speed greater than the first
speed. The interface integrated circuit is adapted for providing a
predetermined electrical load on the memory bus independent of a
number of the DRAM integrated circuits to which the interface
integrated circuit is electrically coupled. The stacked memory
chips are constructed in such a way that eliminates problems like
signal integrity while still meeting current and future memory
standards. However, the above prior art fails to assist the
embedded designers to design a compact main circuit board with plug
and play high density memory channels for many embedded computing
systems.
[0009] Yet another prior art, U.S. Pat. App. No. 20110149499 A1
titled "DIMM Riser Card With An Angled DIMM Socket And A Straddled
Mount DIMM Socket" filed by International Business Machines
Corporation discloses a DIMM riser card that includes a PCB having
a first edge, a second edge, and one or more faces. The first edge
of the PCB is configured for insertion into a main board DIMM
socket. The first edge includes electrical traces that electrically
couple to a memory bus. The DIMM riser card includes an angled DIMM
socket mounted on one face of the PCB, where the angled DIMM socket
is configured to accept a DIMM at an angle not perpendicular to the
PCB and electrically couple the DIMM to the memory bus. The DIMM
riser card includes a straddle mount DIMM socket mounted on the
second edge of the PCB. The straddle mount DIMM socket is
configured to accept a DIMM and electrically couple the DIMM to the
memory bus through the electrical traces on the first edge of the
PCB. However, the above prior art fails to assist the embedded
designers to design a compact main circuit board with plug and play
high density memory channels for many embedded computing
systems.
[0010] Hence there exists a need for a plug and play, flexible
high-speed memory module that can be placed with different
configuration on a main circuit board to save the surface area of
the main circuit board in many embedded systems. The needed plug
and play, flexible high-speed memory module would be able to
support the traditional memory-down approach and other
architectures. Further the needed plug and play, flexible
high-speed memory module would assist in the optimized routing of
the memory channels, and other high speed SerDes on a main PCB of
an embedded system and would also provide improved signal integrity
for those signals. Furthermore, the needed plug and play, flexible
high-speed memory module would allow the designers to place the
DIMMs in various positions, which would allows the designers to
optimally design thermal management and mechanical enclosures to
the embedded systems.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention relates to a flexible high-density
memory module for use with a number of electronic computing
devices. The flexible high-density memory module includes an
interposer having a number of interposer interconnects supported on
a first substrate. The interposer interconnects are configured to
form one or more connection with a number of processor
interconnects supported on a main rigid printed circuit board of
the electronic computing devices. The flexible high-density memory
module further includes a controller supported on the first
substrate, a number of SDRAM modules operably arranged on a second
substrate and one or more conductive traces supported on a flexible
substrate having a first end and a second end, each having a number
of connectors, for forming an electrical connection between the
interposer supported on the first substrate and the SDRAM modules
supported on the second substrate. The controller and the
interposer supported on the first substrate is configured to
electrically connect to the processor interconnects supported on
the main rigid printed circuit board of the electronic computing
device to provide a plug and play, flexible, high density memory
channels of desired capacities utilizing the SDRAM modules
supported on the second substrate.
[0012] The first substrate supporting the interposer and the
controller is a first rigid printed circuit board, which supports
the interposer and the controller on one side of the first rigid
printed circuit board or on opposite sides. Further the second
substrate supporting the SDRAM modules is a second rigid printed
circuit board, which is provided with a large surface area compared
to the first rigid printed circuit board for supporting the
high-density arrangement of the SDRAM modules based on a memory
down architecture. The flexible substrate supporting the conductive
traces is a flexible printed circuit board with the number of
connectors at the first end of the conductive traces connects to
the interposer and the controller supported on the first substrate
and the connectors at the second end of the conductive traces
connects to the SDRAM modules supported on the second substrate.
The controller supported on the first substrate communicates with
the SDRAM modules supported on the second substrate through the
conductive traces supported on the flexible substrate. The SDRAM
modules supported on the second substrate forms a dual in-line
memory module (DIMM) of desired capacity, capable of operating at a
desired frequency. Further, the flexible high-density memory module
can be used as a plug and play memory channels for the electronic
computing devices. The flexible substrate enables a parallel,
perpendicular or angular placement of the SDRAM modules over the
main rigid printed circuit board of the electronic computing device
for optimal utilization of a surface area, efficient thermal
design, efficient routing of conductive traces of SERDES channels,
improved heat dissipation and improved performance of the
electronic computing device.
[0013] The present invention further relates to an electronic
computing device having a processor having a number of processor
interconnects supported on a main rigid printed circuit board, a
number of conductive paths provided on the main rigid circuit board
to enable connections between the processor and a number of
components via the processor interconnects and a flexible high
density memory module. The flexible high density memory module
includes an interposer and a controller supported on a first
substrate configured to form at least one connection with the
processor interconnects, a number of SDRAM modules arranged on a
second substrate and a flexible substrate supporting the conductive
traces for forming an electrical connection between the interposer
interconnects and the SDRAM modules. The processor communicates
with the SDRAM modules through the conductive traces provided on
the flexible substrates. The flexible substrate of the flexible
high-density memory module enables a parallel, perpendicular and
angular placement of the SDRAM modules arranged on the second
substrate over a plane of the main rigid printed circuit board.
This arrangement allows the embedded designers to optimize a
surface area of the main rigid printed circuit board by placing the
SDRAM modules on the second substrate over the main rigid printed
circuit board. The flexible substrate, of the flexible high-density
memory module, connecting the first substrate to the second
substrate enables an optimal surface area utilization of the main
rigid printed circuit board, an optimal heat dissipation from the
SDRAM modules, an optimal performance of the SDRAM modules and an
optimal routing and performance of the SERDES channels associated
with the main rigid printed circuit board.
[0014] A primary feature of the invention provides a flexible
high-density memory module having rigid-flex architecture for
optimizing a surface area of the main PCB of an embedded computing
device.
[0015] A second feature of the present invention provides a plug
and play flexible high-density memory module for embedded computing
devices.
[0016] A third feature of the present invention provides a flexible
high-density memory module having a first rigid substrate having a
small area supporting an interposer and a controller and a second
rigid substrate supporting SDRAM modules and a flexible PCB
connecting the first rigid substrate and a second rigid
substrate.
[0017] Another feature of the present invention provides a plug and
play, flexible, high-density memory channels of desired capacities
that can be plugged into the main circuit board of the embedded
computing devices in parallel, perpendicular or at an angle with a
plane of the main circuit board.
[0018] Another feature of the present invention provides a plug and
play, flexible, high-density memory channels that enable the
embedded designers to design the main rigid printed circuit board
of the embedded computing devices with minimum 30% savings in the
surface area.
[0019] Another feature of the present invention provides a plug and
play, flexible, high-density memory channels that enable the
embedded designers to design optimal routing channels on the main
rigid printed circuit board and to achieve optimal performance of
the SERDES channels associated with the main rigid printed circuit
board of the embedded computing devices.
[0020] These together with other features of the invention, along
with the various features of novelty, which characterize the
invention, are pointed out with particularity in the disclosure.
For a better understanding of the invention, its operating
advantages and the specific objects attained by its uses, reference
should be had to the accompanying drawings and descriptive matter
in which there are illustrated preferred embodiments of the
invention. In this respect, before explaining at least one
embodiment of the invention in detail, it is to be understood that
the invention is not limited in its application to the details of
construction and to the arrangements of the components set forth in
the following description or illustrated in the drawings. The
invention is capable of other embodiments and of being practiced
and carried out in various ways. Also, it is to be understood that
the phraseology and terminology employed herein are for the purpose
of description and should not be regarded as limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The figures which accompany the written portion of this
specification illustrate embodiments and method(s) of use for the
present invention, an Improved Walking Stick, constructed and
operative according to the teachings of the present invention.
[0022] FIG. 1 is a printed circuit board with an integrated
high-density memory down architecture, according to a prior art of
the present disclosure;
[0023] FIG. 2 illustrates a schematic showing a conventional memory
down architecture of a high-density dual in line memory module
(DIMM), according to a prior art of the present disclosure;
[0024] FIG. 3 is a schematic diagram showing the present flexible
high-density memory module for use with a number of electronic
computing devices, according to a preferred embodiment of the
present disclosure;
[0025] FIG. 4 is a schematic diagram showing the present flexible
high-density memory module for use with the electronic computing
devices, according to an alternate embodiment of the present
disclosure;
[0026] FIG. 5 is a schematic diagram showing the present flexible
high-density memory module for use with the electronic computing
devices, according to another alternate embodiment of the present
disclosure;
[0027] FIG. 6 illustrates a microstrip test structure of a flexible
substrate associated with the present flexible high-density memory
module to analyze the effect of bend angle and bend radius of the
flexible substrate on signal integrity and radiated emission from
the present flexible high-density memory module, according to an
embodiment of the present disclosure;
[0028] FIG. 7 is a graph showing an insertion loss of the present
flexible high-density memory module for different bend angles of
the flexible substrate under a constant bend radius, according to
an embodiment of the present invention;
[0029] FIG. 8 is a graph showing an insertion loss of the present
flexible high-density memory module for different bend radii of the
flexible substrate under a constant bend angle, according to an
embodiment of the present invention;
[0030] FIG. 9 is a graph showing a normalized radiated emission at
a distance for different bend angles of the flexible substrate,
according to an embodiment of the present invention;
[0031] FIG. 10 is a graph showing a normalized radiated emission at
a distance for different bend radii of the flexible substrate,
according to an embodiment of the present invention;
[0032] FIG. 11A shows a three-dimensional model of the present
flexible high-density memory module, according to a preferred
embodiment of the present invention;
[0033] FIG. 11B shows the first substrate supporting the interposer
and the controller, solder balls, interposer, the flexible
substrate and the second substrate supporting the SDRAM modules are
represented without simplifications in full 3D detail, according to
an embodiment of the present invention;
[0034] FIG. 12 shows a three-dimensional model showing a breakout
region of the main rigid printed circuit board and an interposer of
the flexible high-density memory module, according to a preferred
embodiment of the present invention;
[0035] FIG. 13 shows a worst-case eye diagram and BER contour for
one victim on the Flex-DIMM at 2666 MT/s without considering the
crosstalk, according to an embodiment of the present invention;
[0036] FIG. 14 shows a worst-case eye diagram and BER contour for
one victim on a Reference Design at 2666 MT/s without considering
the crosstalk, according to an embodiment of the present
invention;
[0037] FIG. 15A shows an insertion loss and far-end crosstalk for
one bit of the reference design and the same bit on the flex
interposer of the present flexible high-density memory module,
according to an embodiment of the present invention; and
[0038] FIG. 15B shows an insertion loss and far-end crosstalk for
one bit on the flex interposer of the present flexible high-density
memory module, according to an embodiment of the present
invention.
DETAILED DESCRIPTION
[0039] In the following discussion that addresses a number of
embodiments and applications of the present invention, reference is
made to the accompanying drawings that form a part hereof, and in
which is shown by way of illustration specific embodiments in which
the invention may be practiced. It is to be understood that other
embodiments may be utilized, and changes may be made without
departing from the scope of the present invention. The embodiments
of the present disclosure described below are not intended to be
exhaustive or to limit the disclosure to the precise forms
disclosed in the following detailed description. Rather, the
embodiments are chosen and described so that others skilled in the
art may appreciate and understand the principles and practices of
the present disclosure.
[0040] Further, various inventive features are described below that
can each be used independently of one another or in combination
with other features. However, any single inventive feature may not
address any of the problems discussed above or only address one of
the problems discussed above. Further, one or more of the problems
discussed above may not be fully addressed by any of the features
described below. The following embodiments and the accompanying
drawings, which are incorporated into and form part of this
disclosure, illustrate one or more embodiment of the invention and
together with the description, serve to explain the principles of
the invention. To the accomplishment of the foregoing and related
ends, certain illustrative aspects of the invention are described
herein in connection with the following description and the annexed
drawings. These aspects are indicative, however, of but a few of
the various ways in which the principles of the invention can be
employed and the subject invention is intended to include all such
aspects and their equivalents. Other advantages and novel features
of the invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the drawings.
[0041] Further the following section summarizes some aspects of the
present disclosure and briefly introduces some preferred
embodiments. Simplifications or omissions in this section as well
as in the abstract or the title of this description may be made to
avoid obscuring the purpose of this section, the abstract and the
title. Such simplifications or omissions are not intended to limit
the scope of the present disclosure nor imply any limitations.
[0042] The present invention relates to flexible high-density
memory modules for use with a variety of electronic computing
devices such as, but not limited to, single board computers (SBCs),
advanced driver assistance systems (ADAS), infotainment systems and
other embedded systems utilizing a single board system having a
hardware package and an embedded software package employed in a
number of industries. In addition, the present flexible
high-density memory modules are designed for use with many embedded
computing systems used for specialized purposes such as
high-performance computing. The present flexible high-density
memory modules enable efficient space utilization in the main
circuit board of the embedded computing systems. Further the
present flexible high-density memory modules provide optimal
performance of the memory modules along with minimal power
consumption compared to the existing memory modules utilizing the
memory down architecture. The present flexible high-density memory
modules enable the designers to free up an additional surface area
of 30% or more on the conventional main circuit boards with
efficient placement of the high performance memory modules over the
main circuit boards. Further, the present arrangement of the
flexible high-density memory modules enables the designers to
effectively design the conductive traces for the other signals such
as a Serializer-Deserializer (SERDES) including PCIE-gen3, Ethernet
10GBASE-KR, SATA- III, USB3, etc. to route through the printed
circuit board (PCB) without increasing the layer-count to meet the
cost-target of the PCB and performance of these signals at the same
time.
[0043] FIG. 1 shows an exemplary printed circuit board 10 with an
integrated high-density memory channel 20 in a high-density
memory-down configuration, according to a prior art of the present
disclosure. The printed circuit board 10 of the prior art forms an
exemplary board design of a variety of embedded computing systems
such as embedded computers used for a variety of applications, such
as but not limited to, high performance computing, advanced driver
assistance systems, infotainment systems, etc. Modern computers and
other embedded computing systems utilize the high-density memory 20
in a memory-down configuration to increase the memory capacity and
density of the memory modules on the printed circuit board 10. Some
embedded systems utilize the traditional SDRAM dual in-line memory
modules (DIMMs) 20 to achieve high-density and capacity of the
memory modules. FIG. 1 shows an example of double data rate fourth
generation (DDR4) high-density memory channels with 36-SDRAMs 20 on
the PCB 10 of an embedded computing system. The DDR4 SDRAMs 20
consumes more than 30% of the real-estate on the PCB 10 leaving
hard chance for other signals such as SERDES, including PCIE-gen3,
Ethernet 10GBASE-KR, SATA-III, USB3, to route through the PCB 10
without increasing the layer-count to meet the cost-target of the
PCB 10 and performance of these signals at the same time. In
addition, the space requirement for the placement of the
traditional SDRAM dual in-line memory modules 20 on the main
printed circuit board 10 restricts the designers from optimally
designing the other components such as the SERDES including
PCIE-gen3, Ethernet 10GBASE-KR, SATA- III, USB3, etc., within the
limited real-estate of the main printed circuit board 10. This
affects the overall cost versus performance of the embedded
computing systems. In some conventional double layer PCB designs,
the designers optimize the performance of the embedded computing
systems by routing the conductive traces for the SERDES through the
PCB 10 by increasing the layer-count and surface area of the PCB
10. The designers has to further take into account the factors such
as the cost-target of the PCB 10 and performance of these signals
at the same time while designing the main printed circuit board 10
of these modern embedded computing systems.
[0044] FIG. 2 illustrates a schematic showing a conventional
memory-down configuration of a high-density dual in line memory
module (DIMM) 20, according to a prior art of the present
disclosure. The conventional memory-down configuration of the
high-density dual in-line memory module (DIMM) 20 includes
arrangement of a number of SDRAM modules 22 on a pair of sides of a
rigid printed circuit board 24 with a controller 26 on one side for
communicating with the processor of the embedded computing systems.
The rigid printed circuit board 24 with the SDRAM modules 22
arranged in the conventional memory-down configuration to form the
high-density dual in-line memory module 20 is configured to fit
into the slots provided on the main printed circuit boards of the
embedded computing systems and the PCBs of other conventional
computers. The above conventional arrangement of the SDRAM modules
22 in the conventional memory-down configuration limits the
capacity of the plug and play high-density dual in-line memory
module 20, as the size of the rigid printed circuit board 24 cannot
be increased beyond the preset standards. In some conventional main
printed circuit board designs, special sockets are provided to
allow DIMMs to be mounted vertically, or at an angle or even
parallel to the system board. In addition, with this arrangement of
the DIMMs, as the speed of memory devices increases the electrical
performance of such DIMM sockets becomes inadequate. Furthermore,
the elongated DIMM sockets provided on the main printed circuit
boards provides almost no room for routing the conductive traces
for the SERDES through the PCB. Hence, in order to optimally design
the conductive traces for the SERDES through the PCB, the size of
the PCB is increased, which in turn affects the overall cost of the
PCB and in turn the embedded computing device utilizing the
PCB.
[0045] FIG. 3 is a schematic diagram showing the present flexible
high-density memory module 100 for use with a number of electronic
computing devices, according to a preferred embodiment of the
present disclosure. The present flexible high-density memory module
100 is configured to use with a variety of electronic computing
devices such as computers and other single board embedded computing
systems. According to a preferred embodiment, the present flexible
high-density memory module 100 includes an interposer 102 having a
number of interposer interconnects supported on a first substrate
104. The interposer interconnects are configured to form a
connection with a number of processor interconnects supported on a
main rigid printed circuit board of the electronic computing
devices. The present flexible high-density memory module 100
further includes a controller 106 supported on the first substrate
104. In some instance, the controller 106 and the interposer 102
are supported on one side of the first substrate 104. In some other
instances, the controller 106 and the interposer 102 are supported
on opposite sides of the first substrate 104. According to a
preferred embodiment, the first substrate 104 supporting the
interposer 102 and the controller 106 is a first rigid printed
circuit board. The first substrate 104 supporting the interposer
102 and the controller 106 is configured to connect with the
processor interconnects provided on the main rigid printed circuit
board of the electronic computing devices to communicate with the
processor of the electronic computing devices.
[0046] The present flexible high-density memory module 100 further
includes a number of SDRAM modules 108 operably arranged on a
second substrate 110. In a preferred embodiment, the second
substrate 110 supporting the SDRAM modules 108 is a second rigid
printed circuit board. In a preferred embodiment, the SDRAM modules
108 are arranged on the second rigid printed circuit board 110
using the high-density memory-down configuration to form a
high-density dual in-line memory module (DIMM). The arrangement of
the SDRAM modules 108 away from the main rigid printed circuit
board, on the second substrate 110, enables the designers to
provide proper heat transfer channels or ventilation for the proper
cooling of the SDRAM modules 108, which in turn improves the
performance of the present flexible high-density memory module 100.
The controller 106 and the interposer 102 supported on the first
substrate 104 is electrically connected to the SDRAM modules 108
supported on the second substrate 110 using a number of conductive
traces 114 supported on a flexible substrate 112. The conductive
traces 114 supported on the flexible substrate 112 includes a first
end and a second end, each end having a number of connectors for
forming an electrical connection between the interposer 102
supported on the first substrate 104 and the SDRAM modules 108
supported on the second substrate 110. In a preferred embodiment,
the flexible substrate 112 supporting the conductive traces is a
flexible printed circuit board. The connectors provided at the
first end of the conductive traces 114 connects to the interposer
102 and the controller 106 supported on the first substrate 104.
The connectors provided at the second end of the conductive traces
114 connects to the SDRAM modules 108 supported on the second
substrate 110. Thus the flexible substrate 112 or the flexible
printed circuit board connects the first rigid printed circuit
board or the first substrate 104 supporting the interposer 102 and
the controller 106 to the second rigid printed circuit board or the
second substrate 110 supporting the SDRAM modules 108.
[0047] The controller 106 and the interposer 102 supported on the
first substrate 104 is configured to electrically connect to the
processor interconnects supported on the main rigid printed circuit
board of the electronic computing device to provide a plug and
play, flexible, high density memory channels of desired capacities
utilizing the SDRAM modules 108 supported on the second substrate
110. The present flexible high-density memory module 100 is
available with high performance of DDR4 and LPDDR4 high-density
SDRAM modules 108, which can be utilized by the embedded computing
systems to provide top-notch performance for efficient functioning
of the embedded applications such as in high performance computing,
SBCs, ADAS, etc. Further, the present flexible high-density memory
module 100 follows a rigid-flex PCB technology with high-density
high-performance DDR4 and LPDDR4 memory modules or SDRAM modules
108 supported on a separate second substrate 110, which can be
easily placed parallel to and over the main rigid printed circuit
board of the electronic computing devices or embedded systems,
without any mechanical constraints of the connector 106, as with
the conventional prior arts systems of FIG. 1 and FIG. 2. In some
embodiments of the present invention, the first substrate 104
supporting the interposer 102 with the interposer interconnects is
placed under the CPU/GPU/FPGA and the processor interconnectors are
connected to the respective interposer interconnects, which further
connects to the SDRAM modules 108 supported on the second substrate
110 using the flexible substrate 112. In some instances, the
present flexible high-density memory module 100 is utilized as plug
and play memory channels, which enables the embedded designers to
design the main rigid printed circuit board of the electronic
computing device with shortest design-cycle time.
[0048] FIG. 4 is a schematic diagram showing the present flexible
high-density memory module 100 for use with the electronic
computing devices, according to an alternate embodiment of the
present disclosure. The flexible substrate 112 or the flexible
printed circuit board connecting the first rigid printed circuit
board or the first substrate 104 supporting the interposer 102 and
the controller 106 and the second rigid printed circuit board or
the second substrate 110 supporting the SDRAM modules 108 enables
the circuit designers to achieve different configurations with the
present flexible high-density memory module 100. FIG. 3 disclose a
parallel arrangement of the second rigid printed circuit board or
the second substrate 110 supporting the SDRAM modules 108 above the
main rigid printed circuit board, whereas FIG. 4 disclose the
arrangement of the second rigid printed circuit board or the second
substrate 110 supporting the SDRAM modules 108 at right angles to
the first substrate 104 supporting the interposer 102 and the
controller 106. In the arrangement disclosed in FIG. 4, the
flexible substrate 112 is formed with a bend angle at around 90
degrees and the second substrate 110 supporting the SDRAM modules
108 is kept perpendicular to the main rigid printed circuit board
of the electronic computing device. In an alternate embodiment of
the present invention, as in FIG. 5, the flexible substrate 112 is
formed with a bend angle at around 180 degrees and the second
substrate 110 supporting the SDRAM modules 108 is kept parallel to
the main rigid printed circuit board of the electronic computing
device. In all the above types of arrangements, the second
substrate 110 supporting the SDRAM modules 108 is flexibly attached
to the processor interconnects provided on the main rigid printed
circuit board of the electronic computing device. In all the above
arrangements, the SDRAM modules 108 are placed on the second
substrate 110 or the second rigid printed circuit board according
to a memory-down architecture to form a high-density dual in-line
memory module. However, the present flexible high-density memory
module 100 supports other types of memory architectures as the
second substrate 110 or the second rigid printed circuit board is
kept away from the main rigid printed circuit board of the
electronic computing device. The resulting design of the main rigid
printed circuit board of the electronic computing device with
separate placement of the SDRAM modules 108 in the present flexible
high-density memory module 100 allows the designers to utilize the
space, which normally being used for placing the SDRAM modules 108,
for better routing of SERDES channels such as the Ethernet 40G,
SATA, PCIE-gen3/4, HDMI, etc. Furthermore, the present flexible
high-density memory module 100 enables the designers to come up
with better thermal design of the main rigid printed circuit board
of the electronic computing device. In addition, with proper
selection of the bend angle and bend radii of the flexible
substrate 112 connecting the SDRAM modules 108 placed on the second
substrate 110 and the interposer 102 and the controller 106
supported on the first substrate 104, better signal transmission
between the SDRAM modules 108 and the processor is achieved.
[0049] According to a preferred embodiment, a surface area of the
first substrate 104 supporting the interposer 102 and the
controller 106 is considerably smaller than the surface area of a
conventional high-density dual in-line memory module (DIMM) 20 used
in the prior arts. This allows the circuit designers and
fabricators to design and fabricate the main rigid printed circuit
board of the electronic computing devices with a minimal slot area
for accommodating the present flexible high-density memory module
100 of desired capacity. The present flexible high-density memory
module 100 enables the designers to save 30% or more surface area
on the main rigid printed circuit board of the electronic computing
devices compared to the conventional design of the main rigid
printed circuit board with the conventional memory-down
configuration of the high-density dual in-line memory modules
(DIMM) supported on the slots provided on the main rigid printed
circuit board. The additional real-estate space saved on the main
rigid printed circuit board of the electronic computing devices, by
using the present flexible high-density memory module 100, is
utilized for the efficient design and layout of the conductive
traces of the SERDES channels on the main rigid printed circuit
board of the electronic computing devices. The efficient
utilization of the surface area of the main rigid printed circuit
board of the electronic computing devices utilizing the present
flexible high-density memory modules 100 enables cost optimization
on the main rigid PCB. The present flexible high-density memory
modules 100 further allows the designers to design an efficient,
compact main rigid printed circuit board of the electronic
computing devices with an heat management system, which further
improves the performance and overall operating life of the
electronic computing devices.
[0050] FIG. 6 illustrates a microstrip test structure of the
flexible substrate 112 associated with the present flexible
high-density memory module 100 to analyze the effect of bend angle
and bend radius of the flexible substrate 112 on signal integrity
and radiated emission from the present flexible high-density memory
module 100, according to an embodiment of the present disclosure.
The bending of the flexible substrate 112 connecting the SDRAM
modules 108 placed on the second substrate 110 and the interposer
102 and the controller 106 supported on the first substrate 104, in
some instances, affects the signal integrity and radiation
emission. The present analysis on the effects of the signal
integrity and radiation emission due to the bend angle (PhiB) and
bend radius (RB) of the flexible substrate 112 is performed by
considering microstrip routing method for the conductive traces
within the flexible substrate 112. As the microstrip routing
deliver the worst performance in terms of both signal integrity and
radiation emission, the actual performance of the flexible
substrate 112 is considered better than the present analysis
results. The bending of the flexible substrate 112 is simulated
using a geometric multilayer bending feature in a 3D modeler, which
uses flat layout and automatically stretches the metal and
dielectric layers in such a way that co-located points in the flat
layout remain co-located, without considering the mechanical
characteristics on the metal and dielectric layers due to bending.
The controller 106 supported on the first substrate 104
communicates with the SDRAM modules 108 supported on the second
substrate 110 through the conductive traces, bend at a certain
bending angle with a certain bend radii, supported on the flexible
substrate 112.
[0051] FIG. 7 is a graph showing an insertion loss of the present
flexible high-density memory module 100 for different bend angles
of the flexible substrate 112 under a constant bend radius, and
according to an embodiment of the present invention. The insertion
loss of the present flexible high-density memory module 100 is
determined with bend angles 10, 50, 90, 130 and 170 degrees with
constant bend radii. From the graph, it is clear that the bend
angle doesn't have a significant influence on the insertion loss of
the flexible substrate 112 in form of a bent microstrip. Similarly,
FIG. 8 is a graph showing an insertion loss of the present flexible
high-density memory module 100 for different bend radii of the
flexible substrate 112 under a constant bend angle, and according
to an embodiment of the present invention. From the graph, it is
clear that the bend radii do not have a significant influence on
the insertion loss of the flexible substrate 112 in form of the
bent microstrip.
[0052] FIG. 9 is a graph showing a normalized radiated emission at
a distance of at least 3 meters from the bend microstrip of the
flexible substrate 112 with different bend angles, according to an
embodiment of the present invention. In order to analyze the
emission from the microstrip flexible substrate 112, a farfield
probe is kept at 3 m distance away from the bend and the absolute
electric field strength in that location is recorded. FIG. 10 is
another graph showing the normalized radiated emission at a
distance of 3 meters for different bend radii of the flexible
substrate 112, according to an embodiment of the present invention.
The analysis assumes a 1 W excitation at every frequency and a
perfect termination of the trace at both ends. The measurements
were carried out with bend angles of 10, 50, 90, 130 and 170
degrees with constant bend radii as in FIG. 9 and with bend radii
of 0.5, 1.0 and 1.5 with constant bend angle, as in FIG. 10. The
variation in bend angles with constant radii shows an effect on the
emission levels from the microstrip flexible substrate 112. From
the graph shown in FIG. 9, it is clear that larger bend angles
result in lower emission levels. As the bend angle increases, the
radiated power from the microstrip flexible substrate 112 is
distributed over a larger solid angle, which reduces the radiation
emission towards a particular direction. Similarly, from the graph
shown in FIG. 10, it is clear that the bed radius doesn't have a
significant influence on the radiation emission from the microstrip
flexible substrate 112. Thus, from the above analysis on the effect
of bend radius and the bend angle on the emission levels and
insertion loss of the microstrip flexible substrate 112, the effect
of the bending will be less of a concern for the flexible
high-density memory module 100. However, the emission levels and
insertion loss of the microstrip flexible substrate 112 depends on
the material of the microstrip flexible substrate 112 and routing
constraints.
[0053] Further, a high-fidelity case study of a realistic model of
the present flexible high-density memory module 100 is performed
and its performance is compared to conventional memory-down design
with the same memory density, according to an exemplary analysis of
the present invention. FIG. 11A shows a three-dimensional model of
the present flexible high-density memory module 100, according to a
preferred embodiment of the present invention. FIG. 12 shows a
three-dimensional model showing a breakout region of the main rigid
printed circuit board and the interposer 102 of the flexible
high-density memory module 100, according to a preferred embodiment
of the present invention. The 3D model of the present flexible
high-density memory module 100 shown in FIG. 11A and FIG. 12
consists of the entire channel in one single model. Further in FIG.
11B, the first substrate 104 supporting the interposer 102 and the
controller 106, solder balls, the interposer 102, the flexible PCB
or the flexible substrate 112 and the DIMM PCB or the second
substrate 110 supporting the SDRAM modules 108 are represented
without simplifications in full 3D detail.
[0054] In certain instances, the flexible section or the flexible
PCB or the flexible substrate 112 is about 24 mm long with the bent
section taking up about 15 mm. In certain instances, the flexible
substrate 112 employs two metal layers such as the signal layer and
the ground layer in the flexible region. As can be clearly seen in
FIG. 11B, in the bent section, the signal nets are routed with the
smaller distance to accommodate all signal nets on a single layer.
In order to perform a realistic model analysis of the present
flexible high-density memory module 100, the one-byte lane of the
DQ bus to the SDRAM chip 108, which is the furthest away from the
controller 106 is considered, thus giving a worst-case performance
obtained with the present flexible substrate 112. Further, the
S-parameters are calculated using the TLM solver in CST Studio
Suite.TM., which gives a good broadband performance and allows for
an accurate conformal meshing of both rigid and flexible PCBs
without a large effect of mesh bleeding.
[0055] FIG. 13 shows a worst-case eye diagram and BER contour for
one victim on the Flex-DIMM or the present flexible high-density
memory module 100 with SDRAM modules 108 at 2666 MT/s, without
considering the crosstalk, according to an embodiment of the
present invention. FIG. 14 shows a worst-case eye diagram and BER
contour for one victim on a reference design, which uses a
conventional memory-down configuration with the same memory
density, at 2666 MT/s, without considering the crosstalk, according
to an embodiment of the present invention. When the worst-case eye
diagram and BER contour for one victim on the Flex-DIMM or the
present flexible high-density memory module 100, shown in FIG. 13,
is compared with the same results, shown in FIG. 14, of the
reference design that uses a conventional memory-down configuration
with the same memory density, it is clear that the eye opening is
nearly identical between the Flex-DIMM or the present flexible
high-density memory module 100 and the reference design.
[0056] FIG. 15A shows an insertion loss and far-end crosstalk for
one bit of the reference design and FIG. 15B shows the same bit on
the flex interposer 102 of the present flexible high-density memory
module 100, according to an embodiment of the present invention.
The present flexible high-density memory module 100 with SDRAM
modules 108 forming the high density DIMM arrangement is capable of
offering transfer rates up to 2666 MT/s and more during normal
operation. Higher transfer rates using the present flexible
high-density memory module 100 is achieved by reducing the
cross-talk in the flexible PCB region or the flexible substrate 112
forming electrical connection between the interposer 102 supported
on the first substrate 104 and the SDRAM modules 108 supported on
the second substrate 110. The cross-talk in the flexible PCB region
or the flexible substrate 112 is achieved using multiple layers
according to one or more embodiment of the present invention.
Utilization of three layers or more in the flexible PCB region or
the flexible substrate 112 provides less cross talk in the
stripline routing according to one or more embodiment of the
present invention. Further, increasing the layer count in the
flexible PCB region or the flexible substrate 112 also allow the
designers to increase the separation distance of the signal nets,
thus further reducing cross-talk in the present flexible
high-density memory module 100.
[0057] The present invention further proposes a new design for a
variety of electronic computing devices with a single printed
circuit board computing system having a processor having a number
of processor interconnects supported on a main rigid printed
circuit board, a number of conductive paths provided on the main
rigid circuit board to enable a number of connections between the
processor and a number of different types of components via the
processor interconnects and a flexible high density memory module
100. The flexible high density memory module 100 of the present
electronic computing devices includes an interposer 102 having a
number of interposer interconnects supported on the first substrate
104 configured to form at least one connection with the processor
interconnects, at least one controller 106 supported on the first
substrate 104, a number of SDRAM modules 108 arranged on a second
substrate 110 and a flexible substrate 112 supporting at least one
conductive trace having a first end and a second end, each having a
number of connectors, for forming an electrical connection between
the interposer interconnects and the SDRAM modules 108. The
processor communicates with the SDRAM modules 108 through the
conductive traces provided on the flexible substrates 112. The
flexible high-density memory module 100 is connected to the main
rigid printed circuit board using the interposer interconnects
supported on the first substrate 104. The first substrate 104
supporting the interposer 102 and the controller 106 is a first
rigid printed circuit board, which supports the he interposer 102
and the controller 106 on a same surface and on opposite surfaces.
Further, the present flexible high-density memory module 100 can be
made as a plug and play memory module that can be attached to the
slot provided on the main rigid circuit board of the electronic
computing devices.
[0058] The flexible substrate 112 of the flexible high-density
memory module 100 enables a parallel placement of the SDRAM modules
108 arranged on the second substrate 110 over a plane of the main
rigid printed circuit board, or a perpendicular placement of the
SDRAM modules 108 arranged on the second substrate 110 over a plane
of the main rigid printed circuit board, or an angular placement of
the SDRAM modules 108 arranged on the second substrate 110 over a
plane of the main rigid printed circuit board. However the
arrangement of the second substrate 110 over a plane of the main
rigid printed circuit board depends on the mechanical requirements,
thermal requirements, spacing requirements and the casing design of
the electronic computing devices. Thus the present flexible
high-density memory module 100 optimizes a surface area utilization
of the main rigid printed circuit board by placing the SDRAM
modules 108 on the second substrate 110 over the main rigid printed
circuit board. Further the flexible substrate 112, of the flexible
high-density memory module 100, connecting the first substrate 104
to the second substrate 110 enables an optimal surface area
utilization of the main rigid printed circuit board, an optimal
heat dissipation from the SDRAM modules 108 providing an optimal
performance of the SDRAM modules 108. The flexible high-density
memory module 100 also enables the embedded designers to achieve an
optimal routing and improved performance of the SERDES channels
associated with the main rigid printed circuit board. Further the
SDRAM modules 108 supported on the second substrate 110 can form a
number of dual in-line memory modules (DIMM), arranged based on
memory-down architecture or any other supported architecture, of
desired capacity and capable of operating at a desired frequency.
The present flexible high-density memory module 100 is configured
to function in form of a plug and play memory channel for the
electronic computing devices. The flexible high-density memory
module with multi-layered flexible substrate 112 enables optimal
performance of the SDRAM modules by preventing cross-talk between
the components associated with the main rigid printed circuit
board. Further selection of an optimal bend angle and a bend radius
of the flexible substrate 112 also assist to achieve an improved
performance with the present flexible high-density memory module
100. The flexible substrate 112 further enables optimal performance
of the SDRAM modules 108 by providing optimal heat dissipation with
the optimal selection of the bend angle and the bend radius.
[0059] The present flexible high-density memory module 100 proposes
a new architecture replacing the memory down for embedded systems
such as SBCs, ADAS and infotainment applications requiring
high-density and maximum performance memory channels utilizing DDR4
and LPDDR4 latest technology. The present flexible high-density
memory module 100 is capable of being operated as a plug-n-play
like the conventional socketed DIMM configuration in the above said
embedded computing systems without any mechanical constraints. The
present flexible high-density memory module 100 enables the
embedded designer to optimize the stackups for the main-PCB and the
flexible high-density memory module 100 separately to achieve best
performance for both SERDES and the memory channels independently.
For example, the embedded designers can optimize the stackup with
lower-layer count for the main-PCB for SERDES while separately
optimizing the Flex-DIMM stackup 100 for best single-ended data
signals. The performance of the present flexible high-density
memory module 100 is improved by turning-on the DBI, which is a
critical feature in DDR4 and LPDDR4 to reduce x-talk, and by
increasing the number of layers on the flexible substrate 112 to
enable strip-line routing on the flexible substrate 112, which
further reduces the radiated emission. Further the use of the
present flexible high-density memory module 100 enables the
embedded designers to save at least save 30% of the main-PCB
real-estate, which in turn can be used for SERDES channels and
promotes the cost optimization between the main-PCB and the present
flexible high-density memory module 100.
[0060] Further, it should be noted that the steps described in the
method of use could be carried out in many different orders
according to user preference. The use of "step of" should not be
interpreted as "step for", in the claims herein and is not intended
to invoke the provisions of 35 U.S.C. .sctn. 112, (6). Upon reading
this specification, it should be appreciated that, under
appropriate circumstances, considering such issues as design
preference, user preferences, marketing preferences, cost,
technological advances, etc., other methods of use arrangements,
elimination or addition of certain steps, including or excluding
certain maintenance steps, etc., may be sufficient.
[0061] The foregoing description of the preferred embodiment of the
present invention has been presented for the purpose of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise form disclosed. Many
modifications and variations are possible in light of the above
teachings. It is intended that the scope of the present invention
not be limited by this detailed description, but by the claims and
the equivalents to the claims appended hereto.
* * * * *